EPDM rubbers (ethylene/propylene/diene mixtures) and their sulfonated versions are well known in the art, see U.S. Pat. No. 3,836,511. Neutralized sulfonated EPDM rubbers are disclosed in U.S. Pat. No. 4,147,677 to be mixed with plastics and to be molded into articles having good properties. U.S. Pat. No. 3,642,728 discloses selective sulfonation of sites of olefinic unsaturation in EPDM. The sulfonic acid containing polymers and their sulfonate salts are said to exhibit improved physical properties as compared to their unsulfonated counterparts. Also disclosed in this patent are methods for making ionomers such as by neutralizing the acidic polymers, for instance, by using a metal compound in a solubilized form and adding it to the solution of the acidic polymer with good mixing. The patent also discloses that a sulfonated EPDM is suitable for blending with a variety of resins including polyethylene terephthalate.
U.S. Pat. No. 4,188,351 discloses elastomeric blends, containing neutralized sulfonated elastomeric polymer and polystyrene thermoplastic resin, having improved rheological properties.
U.S. Pat. No. 4,330,447 discloses compositions containing neutralized sulfonated polymer, characterized in having an improved melt flow and a lower coefficient of friction.
In accordance with the Chemical Abstract of Adv. Chem. Ser. 1980, 187 (Ions Polym.), 3-19 (Eng) metal sulfonated groups were introduced in EPDM rubbers by reaction of the residual unsaturation with acetyl sulfate followed by neutralization of the resultant polymeric sulfonic acid with metal acetate. By proper selection of the EPDM backbone and sulfonate content and through the use of a zinc cation it was possible to prepare EPDM based ionomers with excellent mechanical properties and low melt viscosities.
The physical properties of blends of polypropylene with sulfonated EPDM rubber zinc salts were disclosed in European patent application No. EP-56003.